Field of the Invention
The present invention relates to a high-speed printer and the uses of such a printer.
In recent years, printer manufacturers have proposed systems for endless printing of a paper web which allow two-color or two-sided printing.
One known system utilizes two machines in tandem, one for printing in black, the other for printing in blue. The paper web passed directly from one machine to the other, generally under a false floor. The disadvantage of such a technique is the necessity for mobilizing two printers even when the portion of the job requiring two colors is relatively small. Technically, the existence of a long paper loop between the exit of one machine and the entrance into the other prevents the fine registering of both colors, particularly if the paper web is not taut.
More recently, approaches for two-sided printing have been proposed which also use two printers in tandem, but which are disposed along axes at 90.degree. so as to allow the paper web to be turned over by a bar at 45.degree.. The paper may or may not be taut, since there are no excessive requirements for registering both sides in the case of two-sided printing. This approach also has the economic disadvantage of requiring two separate machines. Still, it must be noted that the associated additional cost is more justified than in the case of two-color printing due to the resultant savings in paper (also a factor of two). On the other hand, the "L" configuration consumes floor space and does not integrate well with linear installations of presses, such as those encountered in the industrial shops for which two-sided machines are specifically intended. However, an in-line configuration is possible using a more complex system with 3 turner bars, but without reducing the total length of the line. In the case of a simple one-sided operation, one can always return to two separate printers and maintain the same output in terms of pages per minute, but at the cost of relatively clumsy handling.
Another approach to two-sided printing is proposed in U.S. Pat. No. 4,796,066. Two printing motors are placed in series inside a single printer (the double motor approach). This architecture allows the sharing of certain functions common to both motors, hence a lower cost. However, in the case of simple one-sided printing, one of the motors remains unused and the output in pages per minute is divided in half.